Field of the Invention
The invention lies in the telecommunications field. More specifically, the present invention relates to a method for transferring a call from the active status in a communications network based on ITU-T Standard H.323.
Such a call transfer procedure is known in principle, for example, in the communications network based on ITU-T Standard H.450.2. The term xe2x80x9ccall transfer from the active statusxe2x80x9d thereby means that, when there is a call between a first endpoint A (terminal A) and a second endpoint B (terminal B) in a communications network based on ITU-T H.323, the endpoint A prompts a connection to be set up between the endpoint B and an endpoint C and prompts the connection between the endpoint A and the endpoint B to be released. In this context, the expression xe2x80x9cexisting connectionxe2x80x9d means that logical channels for useful data transmission, i.e. bearer channels or basic channels, are open between the relevant endpoints.
Although such call transfer from the active status is known from communications networks having central call control, such as private branch exchanges or ISDN networks, it cannot be implemented in the same way in a communications network based on ITU-T Standard H.323, that is to say a communications network without central call control.
It is accordingly an object of the invention to provide a method which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which enables setting up a connection, prompted by a first endpoint A when a connection exists between this first endpoint A and a second endpoint B in a communications network based on ITU-T Standard H.323, between the second endpoint B and a third endpoint C and of clearing the connection existing between the first endpoint A and the second endpoint B.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of setting up a connection, prompted by a first endpoint during an existence of a connection between the first endpoint and a second endpoint, in a communications network based on ITU-T Standard H.323, between the second endpoint and a third endpoint, which comprises the following method steps:
transmitting a facility message for call transfer, including an address for a third endpoint, to a proxy function;
transmitting a connection setup message from the proxy function to the third endpoint;
transmitting a call connect message from the third endpoint to the proxy function;
releasing a connection between the first endpoint and the second endpoint; and
prompting, with the proxy function, for a connection to be set up between the second endpoint and the third endpoint.
In such a method, a device at the first endpoint and the proxy function must be able to process call transfer signaling, for example based on ITU-T H450.2. Such a function does not need to be supported at the second endpoint. According to the invention, a facility message for call transfer, including an address for the third endpoint and thus a request for a connection to be set up between the second and the third endpoint, is transmitted from the first endpoint to the proxy function. The proxy function subsequently sets up a signaling connection to he third endpoint and performs signaling between the second and the third endpoint, involving the proxy function. In addition, the proxy function prompts a connection between the second and the third endpoint. Such a connection via bearer channels can be set up either directly between the second and the third endpoint or with the involvement of the proxy function, depending on the network configuration.
In accordance with a concomitant feature of the invention, the connection between the first endpoint and the second endpoint to be released is initiated by the proxy function. Generally, the closure of the bearer channels between the first endpoint and the second endpoint can be prompted either by the proxy function or from the first endpoint.
In an advantageous embodiment, therefore, signaling between endpoints takes place via the proxy function. The bearer channels, however, are opened directly between the endpoints.
If, as indicated above, the second endpoint does not support call transfer signaling based on ITU-T H.450, then call transfer signaling must be supported at the third endpoint.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method of implementing call transfer from the active status in a communications network based on ITU-T Standard H.323, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.